In Internet Protocol (IP) Television (IPTV) networks, two primary requirements must be satisfied by the underlying network in order for services to be delivered effectively: fast restoration and efficient multicast. The fast restoration requirement is needed in order for services to converge quickly in response to a failure. In IPTV networks, restoration is typically required to be performed in less than 50 ms. The efficient multicast requirement is needed in order to control consumption of network resources. In IPTV networks, there may be hundreds of high-bandwidth television channels that need to be distributed from a few content sources to potentially millions of content subscribers and, thus, replication of television channels for multicast purposes must be performed as close to the content subscribers as possible in order to minimize consumption of network resources.
In IP networks, Multiprotocol Label Switching (MPLS) is often used to provide fast restoration capabilities and Protocol Independent Multicast (PIM) is used to provide multicast capabilities. In existing IP networks, however, MPLS and PIM cannot be used together because many problems result. First, the PIM Reverse Path Forwarding (RPF) check does not account for MPLS Label Switched Paths (LSPs). Second, even where the PIM RPF checks are successful, this results in multiple Outgoing Interfaces in the Outgoing Interface List (OIL) for multicast replication, and, consequently, multiple point-to-multipoint (P2MP) LSPs are required, thereby complicating provisioning and restoration processes. Third, network convergence after a link failure would take as long as the combined unicast protocol convergence and subsequent multicast protocol convergence (i.e., on the order of seconds).
As described herein, due to the competing considerations of the MPLS and PIM protocols, MPLS and PIM currently cannot be used together in existing IP networks, and, thus, there is no known IP network implementation which can satisfy these requirements for IPTV networks.